Method of manufacturing a capacitor in a semiconductor device

ABSTRACT

A method of manufacturing a capacitor in a semiconductor device uses a metal as an upper electrode and a lower electrode, and forms a dielectric film in a double structure of a titanium-containing tantalum oxide film and an amorphous tantalum oxide film. Therefore, the invention can secure a sufficient capacitance while improving an electrical characteristic of the capacitor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to a method of manufacturing a capacitorin a semiconductor device. More particularly, the invention relates to amethod of manufacturing a capacitor in a semiconductor device, wherein ametal is used as an upper electrode and a lower electrode, and adielectric film is formed in a double structure of a titanium-containingtantalum oxide film and an amorphous tantalum oxide film, thus securinga sufficient capacitance while improving an electrical characteristic ofthe application.

2. Description of the Prior Art

As a semiconductor device is more highly integrated, the cell size of acapacitor is increasingly reduced, although the capacitance per cellnecessary for a stable operation of a device is not changed. A capacitorusing a tantalum oxide (Ta₂O₅) film, which has been developed as adielectric film, and a polysilicon film as a lower electrode could notsecure a sufficient capacitance.

In order to solve this problem, the lower electrode must be formed of ametal layer to lower the effective thickness or to secure itscapacitance, or a material having a high dielectric constant than atantalum oxide film (∈=25) must be used.

SUMMARY OF THE INVENTION

A method of manufacturing a capacitor in a semiconductor device includesthe steps of forming a plug and a diffusion prevention film on asemiconductor substrate in which a predetermined structure is formed;depositing a Ru film on the entire structure; patterning the Ru film toform a lower electrode; forming a titanium-containing tantalum oxidefilm on the entire structure; thereafter performing an annealingprocess; forming an amorphous tantalum oxide film on thetitanium-containing tantalum oxide film; and depositing a metal layer onthe entire structure to form an upper electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be explained in the following description, taken inconjunction with the accompanying drawing, wherein:

FIG. 1A and 1B are cross-sectional views of a device for explaining amethod of manufacturing a capacitor in a semiconductor device accordingto the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

It is an objective of the disclosed method to provide a method ofmanufacturing a capacitor in a semiconductor device capable of securinga sufficient capacitance, while lowering the effective thickness.

Another objective of the disclosed method is to provide a method ofmanufacturing a capacitor in a semiconductor device capable of improvinga leakage current characteristic.

In the disclosed method, a metal is used as an upper electrode and alower electrode, and a tantalum oxide film in which titanium is addedand an amorphous tantalum oxide film are used as a dielectric film. Thetantalum oxide film in which titanium is added can secure a sufficientcapacitance, and the amorphous tantalum oxide film can improve anelectrical characteristic of the capacitor.

The amorphous tantalum oxide film has a better leakage currentcharacteristic than the crystallized tantalum oxide film, but itincreases the effective thickness. On the other hand, the crystallizedtantalum oxide film has a better leakage current characteristic than theamorphous tantalum oxide film, but it reduces the effective thickness.

The disclosed method will now be described in detail by way of apreferred embodiment with reference to accompanying drawing.

In FIG. 1A, an interlayer insulating film 12 is formed on asemiconductor substrate 11 in which a predetermined structure is formed.Then, a selected portion of the interlayer insulating film 12 is etchedto form a contact hole through which the given region of thesemiconductor substrate 11 is exposed. Next, a polysilicon film isformed on the entire structure so that the contact hole can be filled.Thereafter, the polysilicon film is blanket-over-etched to form a plug13 in which an upper portion of the contact hole remains to apredetermined depth. Then a Ti/TiN film, as a diffusion prevention film14, is formed on the plug 13 within the contact hole. After an oxidefilm 15 is formed on the entire structure, the diffusion prevention film14 etches a given region of the oxide film 15 to expose the diffusionprevention film 14. Next, a Ru film 16 as a lower electrode is formed onthe entire structure. The Ru film 16 is deposited by introducing gaseoustris (2,4-octanedionato) ruthenium into a reaction furnace containing awafer, within which a pressure of about 0.1 Torr to about 10 Torr ismaintained. At this time, an oxygen and NH₃ reaction gas is introducedat a flow rate of about 5 sccm to about 1000 sccm and the wafer withinthe reaction furnace is heated to about 200° C. to about 350° C. The Rufilm 16 is formed in a thickness of about 100 Å to about 500 Å.

Referring to FIG. 1(b), after the Ru film 16 is polished, the oxide film15 is removed. Then, a tantalum oxide film 17 in which Ti is added isformed on the entire structure. After a subsequent annealing process isperformed, a tantalum oxide film 18 is formed. The tantalum oxide film18 is amorphous and is not exposed to an annealing process. Then, a TiNfilm or a Ru film is formed on the entire structure to form an upperelectrode. The titanium-containing tantalum oxide film 17 is formed byvaporizing tantalum ethylate (Ta(OC₂H₅)₅) in a vaporizer within whichthe temperature of tantalum ethylate is maintained at about 170° C. toabout 190° C., oxygen at a flow rate of about 10 sccm to about 1000 sccmas a reaction gas is introduced into the vaporizer, and the tantalumethylate is introduce into a reaction furnace within which Ti flows at arate of about 1 sccm to about 200 sccm. At this time, the reactionfurnace is kept at the pressure of about 0.1 Torr to about 1.2 Torr andthe wafer within the reaction furnace is heated at about 300° C. toabout 400° C.

A subsequent annealing process is performed by two steps: a first stepof performing a N₂O plasma or UV/O₃ process at a temperature of about300° C. to about 500° C. and a second step of performing a rapidannealing process or a reaction furnace annealing process using N₂ gasand O₂ gas at a temperature of about 500° C. to about 700° C. Thetantalum oxide film 18 is formed in a manner that tantalum ethylate ismade in a gas state in a vaporizer within which the temperature oftantalum ethylate is kept at about 170° C. to about 190° C., oxygen at aflow rate of about 10 sccm to about 1000 sccm as a reaction gas isintroduced into the vaporizer, the wafer is heated at a temperature ofabout 300° C. to about 400° C., and tantalum ethylate is then introducedinto the reaction furnace within which Ti is maintained at a pressure ofabout 1 Torr to about 1.2 Torr.

As mentioned above, the disclosed method manufactures a capacitor inwhich a metal is used as an upper electrode and a lower electrode, and adielectric film is formed in a double structure of a titanium-containingtantalum oxide film and an amorphous tantalum oxide film. Therefore, themethod can secure a sufficient capacitance while improving an electricalcharacteristic of the capacitor.

The disclosed method has been described with reference to a particularembodiment in connection with a particular application. Those havingordinary skill in the art and access to the teachings of the disclosurewill recognize additional modifications and applications within thescope thereof.

It is therefore intended by the appended claims to cover any and allsuch applications, modifications, and embodiments within the scope ofthe invention.

What is claimed is:
 1. A method of manufacturing a capacitor in asemiconductor device, comprising the steps of: providing a semiconductorsubstrate in which a predetermined structure is formed; forming a plugand a diffusion prevention film on said substrate to form an entirestructure; depositing a Ru film on the entire structure; thereafterpatterning said Ru film to form a lower electrode; forming atitanium-containing tantalum oxide film on the entire structure;thereafter performing an annealing process; forming an amorphoustantalum oxide film on said titanium-containing tantalum oxide film; anddepositing a metal layer on the entire structure to form an upperelectrode.
 2. The method of claim 1, wherein said Ru film has athickness of about 100 Å to about 500 Å, and is formed by introducinggaseous tris (2,4-octanedionato) ruthenium into a reaction furnacewithin which a pressure of about 0.1 Torr to about 10 Torr ismaintained, said furnace containing a wafer, and heating the wafer toabout 200° C. to about 350° C. 3.The method of claim 2, comprising thesteps of introducing oxygen or NH₃ to the furnace at a rate of about 5sccm to about 1000 sccm as the reaction gas for forming said Ru film. 4.The method of claim 1, wherein said titanium-containing tantalum oxidefilm is formed by providing gaseous tantalum ethylate and introducingoxygen or titanium at a rate of about 1 sccm to about 200 sccm, to areaction furnace containing a wafer, and heating the wafer to atemperature of about 300° C. to about 400° C.
 5. The method of claim 4,comprising the step of maintaining said reaction furnace at a pressureof about 0.1 Torr to about 1.2 Torr.
 6. The method of claim 4,comprising the step of introducing oxygen at a flow rate of about 10sccm to about 1000 sccm.
 7. The method of claim 4, comprising the stepof introducing titanium at a flow rate of about 1 sccm to about 200sccm.
 8. The method of claim 1, wherein said annealing process comprisesa step of performing a N₂O plasma or UV/O₃ process at a temperature ofabout 300° C. to about 500° C., and a step of performing a rapidannealing process or a reaction furnace annealing process using N₂ gasand O₂ gas at a temperature of about 500° C. to about 700° C.
 9. Themethod of claim 1, comprising the step of forming said amorphoustantalum oxide film by introducing gaseous tantalum ethylate(Ta(OC₂H₅)₅) and oxygen at a flow rate of about 10 sccm to about 1000sccm to a reaction furnace containing a wafer, and heating the wafer toa temperature of about 300° C. to about 400° C.
 10. The method of claim9, comprising the step of maintaining said reaction furnace at apressure of about 0.1 Torr to about 1.2 Torr.
 11. The method of claim 1,wherein said upper electrode comprises a Ru film or a TiN film.